Agent containing active substances, and process of preparing same



Patented Jan. 192i:

UNITED; STATES PATENT OFFICE.

' AGENT CONTAINING ACTIVE SUBSTANCES,

AND PROCESS OF PREPARING SAME Mary No Drawing. Application June l'l,1930, Serial No; 461,839

16 Claims. ((123-233) The present invention relates to catalytic massescomprising a carrier having an active substance in the form of more thanone compound associated therewith, and processes of preparing same.

Patent 1,577,187 discloses a process of preparing a catalytic agent byLreating a hydrogel with a dilute solution of an alkalisuch as sodiumhydroxide for a suflicient length of time to enable more or less of thealkali to be adsorbed in the hydrogel, the concentration oi the alkalisolution being insufficient to react with the hydrogel, (for examplebetween 0.02 to 0.2% by weight) separating the hydrogel from thesolution; rinsing it; treating it with a solution of a salt of acatalytically acting metal for a suflicient length of timeto react withthe adsorbed alkali and form a compound capable of being converted intoa catalytically active form; washing the hydrogel so as to remove theexcess catalytic metal salt; and drying it. v

Although the ptqcess of this'patent produces satisfactory and highlyefficient catalytic agents, the catalytically acting substance ispresent'in one form only, that is, as a single compound of the metal,and in a limited amount. This process is not of universal applicationfor the production of a catalytic agent having the catalytically actingsubstance present in more than one form, for example, as compounds ofametal of different valences, or in larger amounts, or as chemicalcombinations of two catalytically active metals; as chromium vanadate.

It has been found that by employing an alkali solution which issufiiciently strong, not only to charge the carrier material, such as ahydrcgel, but also react therewith to a limited extent, and treating thecarrier with such solution for a time suiilcient to enable the alkali tobe adsorbed thereby and also react therewith to a limited degree,followed by treatment with a solution of a salt of a catalytic metalcapable of chemically combining with the alkali to form a catalyst, anddrying without washing it, an active material results which has thecatalytic substance present in more than one form, for example as twodifferent compounds of the" same metal but of different valences.

The process according to the present invention comprises treating acarrier material with a solution oi a reactant substance orprecipitating agent of a concentration greater than 0.25% by weight, soas to fully charge the material, then treating it with a solution or acompound of a metal to be precipitated or of a compound of a metalcapable of being converted by said reactant substance into an activecompound of said metal, which may or may not contain an activator orstimulator substance, in an amount in excess of that required tochemically combine with said reactant substance, and finally dryingwithout washing.- If desired, the carrier material may be treated with asolution of a compound of a metal capable of being converted by areactant substance into an active compound of said-metal and then with asolution of a reactant substance in an amount less than that required tochemically combine with said metal compound, tollowed by drying withoutwashing; Although both processes produce satisfactory products, theformer process is the preferred one.

The present invention comprehends the employment of any carrier.material. It may be any hydrogel or jelly, or gelatinous precipitate asvfor example, the oxides of silicon, germanium,

vtain preferably about 3 to 12 per cent of moisture.

Then again, it may consist of a powdered solid material of any naturewhich is unafiected by heat or chemical reaction to such degree as todestroy its value as a carrier, for example, fullers earth, kieselguhr,gel fines of any kind, and the like. I

The reactant substance precipitating agent with which the carriermaterial is treated may be either a compound capable of beingselectively adsorbed by the carrier material, as for example, a hydroxylbearing compound or one which difiuses into the carrier material withoutbeing. selectively adsorbed thereby, as for instance a non-hydroxylbearing compound. The hydroxyl bearing compound may consist of anaqueous solution of either the hydroxides of the alkali metals, assodium, potassium, lithium, caesium, rubidium; the hydroxides of thealkaline earth metals, as calcium, strontium, and barium; the hydroxidesof the non-metals such as ammonium hydroxide; hydroxyl containing aminessuch as the ethanolamines, mono-, di-,

. and tri-ethanolamines, hydroxylamine; or comsuch as the carbonates ofthe alkali forming metals, and carbamates.

The non-hydroxyl bearing compound'may consist of an aqueous solution ofeither a salt or a metal which,when the carrier material impregnatedtherewith is treated with a solution of a salt of anothermetal, reactstherewith to form an active compound of said other metal, as forexample, salts of the alkalimetals, potassium vanadit'asoluble salts ofsilver, chromium, zinc, palladium, platinum, tin, iron, calcium, copper,nickel, etc.; or non-hydroxyl containing'amines such as aniline and thelike.

The metal compound capable of being converted by a reactant substanceinto an active compound of said metal or compound of a metal to beprecipitated, may be a salt of a metal capable of forming either hydrousoxides or insoluble basic salts upon reaction with said reactantsubstance. The metallic salts which may be used for thispurpose arethose of the metals such as iron, chromium, aluminum, gallium, indium,thorium, copper, cobalt, nickel, silver, gold, beryllium, magnesium,zinc, cadmium, mercury, lead, germanium, tin, titanium, zirconium,cerium, terbium, yttrium, bismuth, molybdenum, tungsten, uranium,manganese, ruthenium, rhodium, palladium,'caesium, iridium, vanadium,and platinum. Of the salts of the metals mentioned, it is preferred touse those of vanadium..

The concentration of the solution of the reactant substance with whichthe carrier material is treated is dependent upon the nature of thecarrier material and the amount of active metal compound required in thefinal product. In the case where the carrier is a hydrogel, and thereactant substance is a hydroxyl bearing compound, the strength of thehydroxyl bearing compound solution should be such as to charge thehydrpgel and also react therewith to a limited extent or to such degreeas to modify its character without destroying the structure. A solutionof a strength ranging from 0.25 to 1% by weight and even as high as 5%by weight has been found to give satisfactory results.

Where the carrier material is a hydrogel and the reactant substance is anon-hydroiwl bearing compound which is chemically inert with respect tothe hydrogel, the strength of the nonhydroxyl bearing compound solutionmay range from 0.5% to by weight or even higher. The same strengths areemployed if the carrier material is other than a hydrogel.

It is to be understood that the concentration of the reactant substancesolution is variable. All that is required to obtain a satisfactoryproduct is that the concentration be more than required'to charge thecarrier material.

The concentration of the solution of the metal compound capable of beingconverted by a reactant substance into an active compound of said metalis dependent upon the amount of active compound requiredin the finalproduct. The solution used should be of a strength slightly in excess ofthat required to chemically combine with the reactant substance.

Where it is desired to produce a product having an activator orstimulator substance present therein, the substance is admixed with thesolution of the metal compound capable of being con- .verted by areactant-substance into an .active to the present invention consists ofgranules .of carrier material having a plurality of series of rings orotherwise localized layers of precipitates of different or variablecolors disposed therein consisting of different compounds of either thesame or difierent metals. The formation of these rings or localizedlayers of precipitates upon and in the granules of the carrier materialis attributed to the Liesegang Ring Phenomenon. It is thought that whena carrier material such as a. hydrogel or jelly which has beenthoroughly washed is immersed in a metallic salt solution, the solutiondiffuses into the jelly or hydrogel without any convection disturbances.On the other hand, when a hydrogel or jelly which has been saturatedwith a solution of a reactant substance such as a hydroxyl bearingcompound is immersed in a metallic salt solution, the metallic solutiondiffuses into the pores of the hydrogel and reacts therewith to form ahydroxide precipi-' form of a ring or layer grows in thickness as moreof the diffusing metallic salt'reacts with the hydroxyl bearing compoundsolution within the pores until it forms a dam or semi-permeablemembrane, through which more of the metallic salt solution is forced byosmotic pressure. this stage some of the molecules of the metallic saltsolution collect about the exterior surfaces of the semi-permeablemembrane of hydroxide precipitate. As the metallic salt solutioncontinues to diffuse into the hydrogel it meets these molecules ofmetallic salt solution retained, about the exterior surfaces of thehydroxide precipitate membrane and forms a supersaturated metallic saltsolution at this point. This supersaturation of the metallic saltsolution causes a portion of the metallic salt to be thrown out ofsolutionand deposited as a layer or ring in close proximity to the ringof semi-permeable hydroxide precipitate while the rest remains insolution until dried. Where the metallic salt solution is.

reaction. Thus, the hydrogel will contain alterhating layers or rings ofthe hydroxide precipitate and'the deposited metallic. salt. After dryingthe hydrogel, the product consists of gel granules having alternatelayers or rings of hydroxide and the dehydrated metallic salt.

This ring formation depends on the particular reactant substance andmetallic salt selected, and the concentration-of the solutions thereof.To form perfect rings the concentration of the solutions must be suchthat there is no greater osmotic pressure outwardly than inwardly withinthe voids or pores of thecarrier material or the reaction will takeplace either in the supernatant solution or on the surface of thecarrier instead of within the voids. In other words, the pressure mustbe great enough to penetrate entirely through the carrier material.

If all of the reactant substance present in the carrier material isadsorbed within the pores, particularly if a hydroxyl bearing compoundas sodium hydroxide is used, a precipitate forms at the spot where theadsorbed hydroxyl ion is cated when the metallic salt comes in contacttherewith, but no rings will form because there is no outward diffusionof the adsorbed alkali. Again, if the alkali is present in an amountmore than enough to be entirely adsorbed, a precipitate will form bothon the walls and within the pores of the carrier material when themetallic salt solution comes in contact with the alkali. Theseprecipitates, however, may be formless because of disturbances inequilibrium.

When the two solutions come in contact within the pores of a carriermaterial no matter whether one is adsorbed or not, the precipitate whichforms may be slightly soluble or be easily peptized, and the diffusionof. this material will obscure the ring effect. In many cases thesoluble re-' action product may have a higher rate of diffusion than oneor both of the reactant solutions.

Furthermore, side reactions may occur producing a precipitate which mayobscure that formed by the reactant substances and the metallic saltsolution. Then again, the presence of activator substances in themetallic salt solution may obscure the ring eiIect'.

Thus, in some instances the product will show a perfect ring effect, inothers an imperfect ring formation, and in still others none at all.

Whether the product shows this ring formation or not is immaterial forit is the presence of two different compounds of the same or difierentmetals which are distributed in the granules of the carrier material inclose proximity to each other that determines its efllciency andactivity.

The product thus obtained is particularly suited for use as a catalystin processes such as the process for making sulphur trioxide by reactingan oxidizing gas with sulphur dioxide in the presence of a catalyst atan elevated temperature. Processes of this nature in which it isemployed as a catalyst show a conversion of sulphur dioxide into sulphurtrioxide of 98.5% or more.

Specific examples of the process are as follows:

Example 1 acid, heating it to almost the boiling point, in-

jecting or blowing sulphur dioxide gas into the mixture until thevanadic oxide has dissolved,

: and then boiling off the excess sulphur dioxide.

The resulting solution is a dark blue color. A carrier material such asa hydrogel of silica, preferably with a dry surface, is immersed in asolution of a hydroxyl bearing compound. as for example sodium hydroxideof about 1% strength by weight, and is allowed to remain therein for asuflicient time to enablethe alkali to be ad-' sorbed and react with thehydrogel to a limited extent but not to such a degree that the structureof the hydrogel is destroyed. Soaking the hydrogel in the sodiumhydroxide solution for a number of hours, say 18 hours, is sufllcient.

The'hydrogel is separated from the sodium hydroxide solution in any.well-known manner as by draining, rinsed once in water, and then placedupon a sieve and allowed to remain there until the water drains from itsexterior surface.

The hydrogel, chargedwith the sodium hydroxide, is next immersed in thesolution of vanadyl sulphate prepared in the manner indicated above.

It is allowed to remain therein until the reaction between the vanadylsulphate and sodium hydroxide is complete. Usually immersion for anumber of hours, say 24 hours, is suflicient. The

strength of-the vanadyl sulphate solution is such that there is a slightexcess after the soaking has been completed. A vanadylsolutioncontaining 0.032! gram per cubic centimeter of water expressed asVzOag'll/ES satisfactory results. Although a vanadyl sulphate solutionof the aforesaid strength is used. it is to be understood that solutionsof a greater or' lesser strength may be employed. l

The hydrogel is then'drained, rinsed once'with water, and dried in anysuitable manner. The

like, porous material termed the -gel. The drying may be effected bypassing 'air at a temperature of 75 to C. over the hydrogel and later ata higher temperature as 300"v to 400 C.

The product thus obtained consists of granules of silica gel having aplurality of series of rings of different colors disposed therein. Oneof the rings is blue. another brown, 'while still other rings are a'vague blend of the two colors, blue and brown. The blue ring consists ofdehydrated 15 drying converts the 'hydrogel into a hard, glassyvanadylsulphate, and the brown ring of the f hydroxide of tetravalent vanadium.That the rings of diiferent colors are present in the gel granules maybe readily determined by subjecting the granules to a brief leachingwith water whereupon the blue ring disappears and colors the water bluewhile thebrown ring remains fixed. Thus, the gel granules containvanadium i of two different valences in the form of compounds oftetravalent and pentavalent vanadium,

and these vanadium compounds are distributed in the gel granules inclose proximity to each other.

Example 2 A carrier material such as a silica hydrogel is treated in thesame manner as in Example 1 but a vanadyl sulphate solution containingan activator substance is used. The vanadyl sul- Example 3 A carriermaterial such as silica hydrogel is treated in the same manner as inExample 1 but in place of sodium hydroxide, a solution of potassiumcarbonate of 1 to 10%. preferably 5%, strength by weight is used.

The product consists of gel granules having a plurality of localizedlayers of precipitates of different compounds of vanadium distributedinclose proximity to each other. The ring effect may. or may not bepresent.

Example 4 A carriermaterial such as a hydrogel of silica, preferablywith a dry surface, is immersed in a solution of ammonium hydroxide ofabout 1% strength by weight, and is allowed to remain droxide iscomplete.

therein for sufllcient time to enable the alkali to be adsorbed andreact with the hydrogel to a limited extent but not to such a degreethat the structure of the hydrogel is destroyed. Soaking thehydrogel inthe ammonium hydroxide solution for-a number of hours, say 18 hours, issumcient.

The hydrogel is separated from the ammonium hydroxide solution in anywell known manner as by draining, rinsed once in water, and then placedupon a sieve and allowed to. remain there until the water drains fromits exterior surface.

The hydrogel charged with ammonium hydroxide, is next immersed in asolution of vanadyl sulphate prepared as described in Example 1. It isallowed to remain therein until the reaction between the vanadylsulphate and ammonium hy- Usually immersion for a number of hours, say24 hours, is suflicient. The strength of the vanadyl sulphate solutionis such that there is a slight excess after the soaking has beencompleted. A vanadyl solution containing 0.0327 gram per cubiccentimeter of water expressed as V205 gives satisfactory results. Al-'though a vanadyl sulphate solution of the aforesaid strength is used, itis to be understood that solutions of a greater or lesser strength maybe employed.

The hydrogel is then drained, rinsed once with water, and dried in anysuitable manner. The drying converts the hydrogel intoa hard,glassylike, porous material termed the gel. The drying may be effectedby passing air at a temperature of 75 to 120 C. over the hydrogel andlater at a higher temperature as 300'to 400 C.

The product thus obtained consists of granules of silica gel having aplurality of series of rings of diiIerent colors disposed therein. Oneof the rings is blue, another brown, while still other rings are a vagueblend of the two colors, blue and brown. The blue ring consists ofdehydrated vanadyl sulphate and the brown ring of the hydroxide oftetravalent vanadium. That the rings of different colors arepresent inthe gel granules may be readily determined by subjecting the granules toa leaching with water whereupon the blue ring disappears and colors thewater blue while the brown ring remains fixed. Thus, the gel granulescontain vanadium of two different valances in the for n of compounds oftetravalent and pentavalent vanadium, and thesevanadium compounds aredistributed in the gel granules inclose proximity to each other.

Example 5 A carrier material consisting of a tightly packed mass offinely divided kieselguhr is placed in a receptacle. An ammoniumhydroxide solution is then introduced into said receptacle in an amountsuiiicient to submerge the kieselguhr. The concentration of the ammoniumhydroxide solution employed is of about 2% strength by weight.

Soaking for a number of hours, for instance 20- hours, is sufficient tofully charge the mass of carrier material. The ammonium hydroxidesolution is then separated from the mass of carrier material as bydraining. r

A solution of vanadium acetate is then introduced into the receptacle inan amount suiflcient' to completely submerge the mass of kieselguhrcharged with ammonium hydroxide. The vanadium salt solution should be ofa concentration such as to be slightly more than that required tochemically combine with all of thealkalir Avana- Example 6 A mass of gelfines of silica is placed in a receptacle in' such manner as to form atightly packed mass. A calcium chloride solution is then introduced intothe receptacle'in an amount sufficient to cover the mass of gel fines.The concentration of calcium chloride solution may vary from 0.1 to 1.0normal. The mass of gel fines is allowed to soak in the calcium chloridesolution for a; number of hours, say 24 hours, whereupon it is separatedtherefrom as by draining.

A sodium ortho-vanadate solution is next introduced into the receptaclein an amount willcient to completely submerge the gel fines. Theconcentration of the sodium vanadate solution is such as to be slightlyin excess of that required to react'with the calcium chloride. A sodiumvanadate solution of about 1 normal gives satisfactory results. Soakingfor a number of hours, say 24 hours, is sufiicient to complete thereaction.

The impregnated carrier material is then Example 7 A silica hydrogel isimmersedimasolution of.

ammonium vanadite and allowed to remain therein for about 24 hours orless. The concentration of the ammonium vanadite solution may range from0.1 to 2 normal. It is preferred to employ a 0.3 N. solution of ammoniumvanadite.

The hydrogel is separated from the ammonium vanadite solution in anywell known manner as by draining, rinsed once in water and then allowedto drain. 5

The hydrogel charged with the ammonium vanadite is next immersed in asolution of chromium chloride, the concentration of which may vary from0.1 to 1 normal. It is preferred to employ a 0.1 N. chromium chloridesolution. Usually soaking for about 24 hours is sumcient to complete thereaction.

The hydrogel is then drained, rinsed once with water and-dried in thesame manner asgiven in Example 1.

The product consists of gel granules having layers of chromic vanaditeand dried chromium chloride distributed in close proximity to eachother.

Example 8 A washed hydrogel of silica issoaked in a 0.3

. normal potassium vanadite solution for a number proximity to eachother.

Where the product obtained according to the process oi! the presentinvention is desired to be used as a catalyst in a contact process formaking sulphur trioxide it is preferred to activate same as by heatingit for several hours at a temperature from 400 to 500 C. in the presenceof sulphur dioxide gas.

Various specified details of procedure and condltions of operation havebeen set forth above for the purpose of giving a clear understanding ofthe process, but the invention is not limited to the exact detailsgiven, as it includes modifications and changes coming within the scopeof the appended claims.

. Having thus described, the invention, what is claimed as new anddesired to be secured by Letters Patent is: V

.- prises impregnating the carrier'material with a solution of aprecipitating agent the concentration of which is sufliciently strong tocharge the carrier material and react therewith to a limited extent,then treating the impregnated carrier with a solution of a compound of ametal to be precipitated, said solution being in excess, and then dryingthe-resulting mass. V

2. The process according toclaim 1 wherein the precipitating agent is ahydroxyl bearing com-' pound. a

3. The process according to claim 1 wherein the precipitating agent is anon-hydroxyl bearing compound.

4. The process of impregnating catalyst carriers with metallic catalyticagents which com prises impregnating a hydrogel with a solution 01 aprecipitating agent the concentration of which is such as to charge thehydrogel by adsorption and react therewith to a limited extent, then thehydrogel is that of silica.

6. The process according to claim 4 whereinthe solution with which theimpregnated hydrogel is treated contains both a compound of a metal tobe precipitated and an activator substance.

'7. The process according toclaim 4 wherein the hydroxylbearingsubstance is'a hydroxide or one of the member of the groupconsisting of alkali metals, alkaline earth metals, and ammonium.

8. The process of impregnating catalyst carriers with metallic catalyticagents which comprises impregnating a hydrogel with a solution of ahydroxide of one of the members of the group consisting of alkalimetals, alkaline earth metals, and ammonium, the concentration of whichis greater than 0.25% by weight. then treating the impregnated hydrogelwith a solution of a compound of a metal to be precipitated, said lastnamed solution being in excess, and then drying the resulting mass. V

9. The process according to claim 8 wherein the solution with which theimpregnated hydrogel is treated contains both a compound of a metal tobe precipitated andan activator substance.

10. The process according to claim 8 wherein the metal compound is asalt of vanadium.

11. The process according to claim 8 wherein the metal compound isvanadyl sulphate- 12. The process of impregnating catalyst carriers withmetallic catalytic agents which comprises impregnating a hydrogel with asolution of a non-hydroxyl bearing substance capable of precipitatingthe metal subsequently used, separating the impregnated hydrogel fromthe solution,-

the non-hydroxyl bearing substance is a salt of ametal capable ofreacting with a salt of another .metal to form an active compound ofsaid other metal.

15. The process according to claim 12 wherein the non-hydroxyl bearingcompound is a salt of chromium and that of the metal compound a salt ofvanadic acid.

16. An agent consisting of a. hard, porous, gel having an activesubstance in the form of a plurality of groups of rings depositedtherein, each group ,having one ring consisting of an active compound oftetravalent vanadium, and another ring consisting of an active compoundof pentavalent vanadium.

GERALD C. CONNOLLY. JEREMIAH A. PIERCE.

